Tumor interstitial fluid: proteomic determination as a possible source of biomarkers

Tumor interstitial fluid (TIF) is formed largely by an imbalance between the forces that govern the filtration of liquid between the luminal and abluminal parts of tumor neo-vessels. TIF is a dynamic solution that varies according to tumor type, and is generally rich in proteins, lipids, and various enzyme-derived substances. These enzyme-derived substances can have important roles as both regulatory and inflammatory factors. Furthermore, the oncotic pressure caused by the presence of these proteins and peptides in TIF leads to a proinflammatory condition in which macrophages produce cytokines such as Interleukins 1 and 6. With the recent advent of proteomics, TIF has been studied extensively and can be used as a source of potential biomarkers for cancer, including breast, ovarian, and head and neck cancer. In the present review, we discuss the process of TIF formation, its composition, the effects of its accumulation, the methods of sampling, and the proteomic analyses performed on it, which make TIF a valuable tool in monitoring several cancer types.